The present invention generally relates to a technical field of a vacuum apparatus; and more particularly, to a vacuum apparatus having a device for conveying a substrate, while standing it at a nearly vertical angle.
Conventionally, a substrate in a horizontal posture is placed on a hand of a substrate conveying robot; and the substrate is conveyed still in the horizontal posture by expanding and shrinking the hand. Alternatively, a substrate in a horizontal posture is placed on a plurality of rollers having rotary axes horizontally arranged to convey it by rotating the rollers, while the horizontal posture is being maintained.
However, in such vacuum apparatuses, as substrates become larger, the required installation area also becomes larger.
Under these circumstances, a vacuum apparatus, which conveys a substrate without being set in a horizontal posture, has recently been proposed. For example, techniques are proposed, in which a substrate fitted into a frame is conveyed in a vertical posture, or conveying rollers are arranged in a line on a bottom wall of a vacuum chamber, and a substrate is placed on the conveying rollers standing to be conveyed in an approximately vertical posture by rotating the conveying rollers.
However, when the substrate is conveyed in the vertical posture, it is feared that the substrate falls down from the conveying rollers. In order to prevent the falling down of the substrate, it is suggested that recessed grooves are provided at peripheral faces of the conveying rollers. When the recessed grooves are provided, however, there is a possibility that the substrate may bump against a wall of the recessed groove during the conveyance, thereby resulting in the substrate being damaged.
See, Japanese Patent Document JP-A 10-265018.